XML External Entity (XXE)-Injection is a type of attack targeting XML processing vulnerabilities in applications. In an XXE attack, an attacker attempts to introduce malicious external entities into XML documents and persuade the application to process these entities. This can lead to security issues, including theft of sensitive data, remote code execution, or denial of services.
Here's a basic explanation of how an XXE attack works:
An attacker manipulates an XML document being processed by the targeted application by inserting malicious external entities into the document. An external entity is a reference to an external resource typically defined in a Document Type Definition (DTD) or XML Schema.
The attacker attempts to coax the application into processing the malicious external entities, for example, by sending a specially crafted HTTP request or XML data to the application.
When the application processes the malicious external entities, it can have various effects, including accessing sensitive files or data on the server, executing remote code, or denying services.
A typical example of an XXE attack is stealing sensitive files, such as the contents of configuration files or password files on the server. Through clever manipulation of the XML document, an attacker can persuade the application to disclose the contents of these files.
To protect against XXE attacks, developers need to carefully examine how XML data is processed in their applications. They should ensure they use secure XML parsers, disable external entities, avoid using XML data directly in conjunction with confidential files or data, and thoroughly validate and filter incoming XML data to remove unwanted entities. Enabling XML schema validation and using Content Security Policies can also help prevent XXE attacks. It's also important for administrators to regularly audit their systems and applications for known XXE vulnerabilities and install security updates to minimize potential attack vectors.
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